Large marine vessels, such as cargo ships and crude oil carriers, as well as service and supply barges and ships, can inflict considerable impact damage to marine facilities in the event of an unexpected loss of power, or under storm or other adverse weather conditions. Various sacrificial impact-absorbing constructions have been proposed for use in these marine and off-shore environments. For example, U.S. Pat. No. 4,398,848 discloses a marine barrier of open tubular construction that is supported by deformable shock-absorbing members. However, the open network tubular frame construction is of metal pipes of various diameters, including those that are relatively small and have little impact energy dissipation capacity. The frame is not meant to be the principal energy absorbing element of the combined structure. There does not appear to be any suggestion that the pipes forming the barrier be filled with any material, or that the tubular barrier construction is to be destructively deformed in order to protect the supporting facility from impact with the vessel. Rather, a series of telescoping cylinders having an internal linking membrane and exterior collar function as axially pivoting shock absorber assemblies. An impact at one position along the horizontally-extending tubular barrier is transmitted to all of the absorbing elements to dissipate the force. The structure disclosed in U.S. Pat. No. 4,398,848 has a limited capability for absorbing an impact that is severe enough to destructively deform the framework. In fact, if the frame members are deformed, the shock-absorbing members may be disabled.
Various other structures have been suggested by the prior art for use in the absorption of impact energy in the marine environment to protect structural facilities. Structures of various shapes, configuration and construction are disclosed that are intended to absorb the force of an impact using resilient and elastically deformable elements. In some structures, linking elements are permanently deformed or broken, with the intention that they must be replaced to return the remaining structure to service with minimal replacement expense. In other structures, resilient elements are intended to receive and absorb or dissipate repeated impacts during normal service. For example, U.S. Pat. No. 5,480,265 to Marshall et al. discloses a tubular structure that relies on the elastic response of a compliant structural assembly that is intended to absorb the kinetic energy of an impact, and then return to its original configuration. While such structures may function to absorb a limited amount of energy, and perhaps deflect a glancing impact, such a unit can collapse under a larger impact force, absorbing little of the kinetic energy of the vessel, with the remaining excess energy being transferred to the underlying marine structure causing permanent damage.
It is therefore an object of this invention to provide a sacrificial impact-absorbing structure and methods for its construction that can be secured to marine facilities to protect them from damage due to the impact of large vessels.
It is another object of this invention to provide a protective structure for use in the marine environment that will undergo plastic deformation throughout the elements of its construction in order to provide the maximum energy absorption in the event of an impact by a marine vessel.
A further object of the invention is to provide an impact-absorbing structure that is reliable, relatively simple in design, economical to construct and easy to install.